The long-term goal of this project is to elucidate the mechanism of cellular immunity and hypersensitivity. Such an understanding may allow the rational manipulation of these processes in certain human diseases in which hypersensitivity contributes to the pathogenesis or where enhanced immunity might prevent or alleviate the disease. Studies include further elucidation of the subgroups of lymphocytes responsible for mediator production and characterization of lymphocyte mediators. Studies on the biochemical changes of macrophages activated by lymphocyte mediators are being pursued. Several mouse lymphocyte mediators have been partially characterized and their action on macrophage activation and control of antibody production are under study. The mechanism of a drug which is a potent inhibitor of delayed hypersensitivity has been partially elucidated and is being used now to further dissect the mechanism of mediator production and release by lymphocytes.